Various means have hitherto been employed for the positive detection of R-waves in an electrocardiogram. The method most generally used comprises passing the frequency band including the R-waves though a filter and generating pulses by a single stable multi-vibrator when a predetermined threshold value is surpassed. Such a method may be effective for performing a simple count of a heart rate, but it is not suitable for reading information including various bits of phase information from electrocardiographic wave patterns, since it cannot recognize the peak phase (time phase) of an R-wave. Further, if arrhythmia or a normal R-wave appears together with the artifact through lung or body movement, a problem arises in that it is difficult to accurately detect and recognize the arrhythmia or normal R-wave due to a change in the wave pattern.